Fibrous materials which include fibers of organic materials such as polyester, polyamide and polyimide; fibers of inorganic materials such as glass, silicon carbide, asbestos, rock wool; and fibers of a simple substance such as carbon have been used as a reinforcing material in the manufacture of a fiber reinforced composite. They are blended or coated with a liquid thermosetting resin, or milled with said resin and molded into a fiber reinforced composite by suitable molding means including compression, transfer, injection, extrusion or lamination with other sheet materials. In that case, however, the surface of the reinforcing material is often smooth, which results in insufficient adhesion to the thermosetting resin. Thus, there was a problem that smooth surface of the reinforcing material gives unsatisfactory strength of molded products.